Thanks for the background. The Gods of fortune or luck are on your side
An LS4 file when exported from a Pro version can be used (and is intended to be used) also for workgroups and passing the file to different users for changing. So in your case, yes, you can make use of that more recent LS4 file. It contains all content, scene data etc, so will give you a much closer version to work with.
Just a reminder then to make use of Lumion's save but also saveAs option so that you have your own version copies rather than relying on the auto-saves. So I would suggest once the LS4 is opened, to then immediately go Files --> Save Scene
and create a new scene/project name so it gets 'savedAs' a new scene.
This is one case where it's not possible (AFAIK) to provide an auto-save backup on exit of scene or application if there's simply no room. However, I'll discuss it with Morten, as it might be something maybe dev can look at, as to maybe providing some warning of lack of file space when opening or closing a scene.
In regard the hardware; I would have to say that you should go back to the supplier, a 100GB for Windows and applications is not a workable drive and should be replaced/upgraded. Was it 100GB or 1000GB, perhaps it's an SSD drive, in which case that could explain the GB size, laptop or desktop?
Please note that Lumion stores all user data files in the \My Documents folders, so that is on "C" drive; this is a default and only option (except for a Windows path redirect workaround). This means you will need to manage file space constantly, Lumion projects (scene and imported models) can get large very quickly.
Once you have your project finalised, I would suggest removing the older update versions of Lumion and just working with v4.0.4. That will free up about 8GB for a start
Also as a reminder to start from today
, using some sort of Backup Utility software tool, making sure the \Lumion sub-folders are definitely backed up to some other storage device.
Note: you can save any LS4 files to other locations such as your "E" drive.
All the best then with recovery, we look forward to seeing the resulting video and images when available.
ps: can you change your forum icon from the standard version icon to the Pro version icon (see your Account, link top of page)